1. Technical Field
The present invention relates generally to an improved data processing system and in particular to a method and apparatus for processing data. Still more particularly, the present invention relates to a method, apparatus, and computer instructions for changing operating frequencies in a system core logic in a data processing system.
2. Description of Related Art
A data processing system contains many different components that are interconnected to each other through a communications system, such as a bus. These components include a processor, a memory, and various input/output (I/O) adapters or components. The processor executes instructions in a fashion regulated by a clock rate. Additionally, other components, such as the bus and memory, also operate at a selected clock rate. An internal clock is provided to regulate and synchronize the operation of these and other components within the data processing system.
Modern data processing systems have system memory architectures that support memory modules with different speeds in the same system. Memory modules may come in various configurations or forms. One currently used memory module configuration is a dual in-line memory module (DIMM). A data processing system may contain DIMMs running at two different memory speeds, such as 333 mHz and 400 mHz. The system core logic, also referred to as an I/O bridge, generates a clock signal used to drive data on the bus in the data processing system. This system core logic normally runs at a default base frequency to allow the system firmware to initialize the memory and other I/O subsystems. When a data processing system has only high speed DIMMs, it is desirable to move the core operating frequency of the system core logic to that of the high speed DIMMs to increase the bandwidth of the system memory. The operating frequency is often set through a basic input/output system (BIOS).
Dynamic switching of the core frequency is hazardous and must be carefully handled to avoid a system crash. The setting of this frequency is made more complicated if the data processing system cannot set the frequency from the BIOS. Additionally, when a data processing system has multiple processors, the possibility of a system crash increases when dynamic switching of the core frequency is attempted.
Therefore, it would be advantageous to have an improved method, apparatus, and computer instructions for dynamically changing the operating frequency of a data processing system to increase the bandwidth of the system memory in the data processing system.